A servo motor is a motor that controls the operation of mechanical components in a servo system; it is a type of auxiliary motor with indirect speed control. Servo motors can control speed and position with very high accuracy, converting voltage signals into torque and speed to drive the controlled object.
A servo motor is a closed-loop servo mechanism that uses position feedback to control its motion and final position. The control input is a signal (analog or digital) representing the commanded position of the output axis.
The motor is paired with some type of position encoder to provide position and speed feedback. In the simplest case, only position is measured. The measured output position is compared with the commanded position (an external input to the controller). If the output position differs from the required position, an error signal is generated, and the motor is then rotated in either direction as needed to move the output shaft to the appropriate position. As the position approaches, the error signal decreases to zero, and the motor stops.
Servo motors are controlled by input signals and can respond quickly. Used as actuators in automatic control systems, they possess characteristics such as low electromechanical time constant and high linearity. They convert received electrical signals into angular displacement or angular velocity output on the motor shaft. Servo motors are broadly classified into DC and AC servo motors. Their main characteristic is that they do not rotate when the signal voltage is zero, and their speed decreases uniformly as the torque increases.
A servo motor is a type of motor that plays a vital role in automated equipment. Its function is to convert voltage signals into torque and speed to drive the controlled object, enabling precise speed and position control. The motor's rotor speed is controlled by the input signal and can respond quickly. In automatic control systems, it serves as an actuator and possesses characteristics such as a small electromechanical time constant, high linearity, and low starting voltage. It can convert received electrical signals into angular displacement or angular velocity output on the motor shaft.
Compared to ordinary motors, servo motors have a faster response speed. In point-to-point rapid positioning motion applications, servo control technology can provide high torque output, giving the system extremely high dynamic response, which greatly surpasses that of motors.
Because frequency converters and servos differ in performance and functionality, their applications also differ:
1. In applications where speed and torque control requirements are not very high, frequency converters are generally used. There are also cases where a position feedback signal is added to the upper level to form a closed loop for position control using frequency converters, but the accuracy and response are not high.
2. In situations requiring strict position control, only servo motors can achieve this. Also, the response speed of servo motors is much faster than that of frequency converters. Servo control is also used in some situations where high precision and response are required. In almost all motion situations where frequency converters can be used for control, servo motors can replace frequency converters. The key reasons are twofold: first, the price of servo motors is much higher than that of frequency converters; second, the power consumption is different: the maximum power of frequency converters can reach several hundred kilowatts or even higher, while the maximum power of servo motors is only tens of kilowatts.
Servo motors are often used as a high-performance replacement for stepper motors. Stepper motors have a built-in output step size, thus possessing an inherent ability to control position. This typically allows them to be used for open-loop position control without any feedback encoder, as their drive signal specifies the number of steps of rotational movement; however, for this to work, the controller needs to "know" the stepper motor's position upon power-up. Therefore, at xxx power-on cycles, the controller will have to start the stepper motor and rotate it to a known position, such as until the end limit switch is activated. This can be observed when turning on an inkjet printer; the controller moves the printer's carriage left and right to establish the final position. Regardless of the initial position upon power-up, the servo motor will immediately rotate to any angle indicated by the controller.
The lack of feedback in stepper motors limits their performance because they can only drive loads within their capacity range; otherwise, step loss under load can lead to positioning errors, and the system may have to be restarted or recalibrated. Servo motors, on the other hand, have encoders and controllers that represent additional cost, but relative to the capacity of the base motor, they optimize overall system performance (achieving best in speed, power, and accuracy). In large systems where powerful motors increasingly account for a significant portion of system cost, servo motors offer an advantage.
